Why is my object in blender bigger by approximately a factor 10 than in my CAD program?
Blender's default unit system is None, so it uses its own "Blender Units" (BU). But if you switch it to Metric in the Scene tab (Properties Editor), you'll notice that nothing changed. And 1 BU will now be 1m.

With Metric enabled, there will be a property available called scene Scale. You can set it to 0.1 to correct the scaling problem (granted, it's really 1:10). But I worry not all exporters will respect it.

So it might be better so Select All objects (A) and scale everything down (S, type 0.1, Enter). Make sure the scaling center is the scene origin (0,0,0), e.g. reset the 3D Cursor (N-sidebar, right-click on one of the 3 value fields and click Reset All to Default Values, or press ShiftC) and use it as Pivot Point (press .).